Operator: We Energies (subsidiary of Wisconsin Energy) Owner: We Power LLC (subsidiary of Wisconsin Energy)
Adding two 615-MW supercritical pulverized coal units to the 1,135-MW Oak Creek Power Plant is part of We Energies’ ongoing master plan to “Power the Future” of Wisconsin well into the 21st century. The new Elm Road Unit 1 went into service in February, and Unit 2 is expected to start operations during the fourth quarter of 2010. With operations marked by high efficiency and low emissions, these new units will provide large amounts of cleaner energy to the Great Lakes area.
Wisconsin’s distinctive culture is characterized by a “can do” attitude that has spawned, among other things, the vibrant port city of Milwaukee, a strong agricultural sector that produces world-class cheeses and beers, and several popular sports teams, including the Green Bay Packers. To keep its economic momentum moving successfully throughout the new century, this Midwestern state will need large amounts of reliable electricity. We Energies’ efforts to meet future energy demands include the current expansion of its Oak Creek Power Plant (OCPP), which covers more than 1,100 acres along the shore of Lake Michigan 20 miles south of Milwaukee.
OCPP is the most thermally efficient generating power plant in Wisconsin, according to Scott Patulski, vice president of fossil operations for We Energies. Currently, the plant has four older coal-fueled generating units, which each has a pulverized coal–fueled boiler and steam turbine generator that entered service from 1959 through 1967. In the late 1980s, four older coal-fueled units, which totaled approximately 500 MW of generating capacity, were retired from the site.
Expanding into the Future
Tom Metcalfe, project director for the Elm Road Units at OCPP and vice president of We Power LLC, described the significance of this new infrastructure for Wisconsin.
“In 2000, Wisconsin Energy, the parent of We Energies, announced our ‘Power the Future (PTF)’ plan that includes investing in advanced power generation, adding renewable energy resources, and improving existing power plants,” Metcalfe said. “The PTF plan is fundamental to the principle of energy self-sufficiency and was announced to help the state of Wisconsin meet its critical energy needs. Because of the complexity and significant financial investment in these major initiatives, our plan has been implemented over several stages.”
Expansion at the Oak Creek site with the construction of two 615-MW supercritical pulverized coal units was essential to the plan’s overall realization. The plan included the objective of expanding or constructing the needed generation at existing brownfield sites, rather than at new, undisturbed greenfield locations.
Keeping the Expansion Project on Deadline
On June 29, 2005, construction of the two new 615-MW units began. The expansion units have become known to many as the Elm Road units in order to distinguish them from the existing four units at Oak Creek, Metcalfe explained.
On February 2, 2010, the new Elm Road Unit 1 passed all of its performance tests and was placed into commercial service. Unit 1 was tested to be among the most efficient plants of its type in the country.
Today, Bechtel Power Corp., the project’s engineering, procurement, and construction contractor, is focusing its efforts on completing the commissioning and testing of Unit 2. The first fire on coal in the Unit 2 boiler was achieved on July 8, and the generator was synchronized to the grid for the first time on July 16. Since then, the unit has operated at up to 100% of its rated capacity.
As this story was being written, Unit 2 was shut down for a scheduled two-week outage. Bechtel was using the time to address punch list items and to remove start-up equipment. The unit is expected to return to service around the middle of September for further tuning and a series of rigorous performance tests.
“As with any two-unit plant, the second unit benefits from the lessons learned on the first, thus shortening the start-up and commissioning schedule,” Metcalfe said. “The guaranteed turnover date for Unit 2 is set for November 28. We expect Bechtel to meet or beat this completion date.”
It’s also not unusual for new plants to experience “teething difficulties” in the first year or two of operation, according to Metcalfe. He predicted that ultimately the units will achieve an annual average equivalent availability factor exceeding 85%.
We Power LLC, a subsidiary of Wisconsin Energy, owns Unit 1 and is leasing the energy output to We Energies. We Energies is responsible for the operation and maintenance of the unit. The leasing arrangement is unique and was developed through enabling legislation.
Overview of Elm Road Units 1 and 2
Both units, which burn Eastern coal, have state-of-the-art air quality control equipment, including selective catalytic reactors to remove nitrogen oxides, baghouse filters to remove particulate matter (ash in the exhaust gas), scrubbers to remove sulfur dioxide (SO2), and a wet electrostatic precipitator to remove sulfuric acid and very fine particulates.
“Unit 1’s emission tests were completed in January 2010, and the results are considered world class,” Metcalfe said. “Actual emissions of particulates, SO2, and the other regulated emissions were tested to be considerably lower than required by the project’s air permit. In the case of SO2, carbon monoxide, and many other regulated substances, the emission rates were a fraction of required permit levels.”
The two units use supercritical boilers that operate at higher temperatures and pressures when compared with conventional subcritical plants. The corresponding steam conditions allow the units to operate at higher thermal efficiencies. In addition, the plant utilizes water from Lake Michigan in a “once-through” cooling system to cool and condense steam from the steam turbine (Figure 1). The cold heat sink allows the plant to extract the maximum possible energy from the steam and hence improves the plant’s thermal efficiency. (See “Deep Excavation Support Systems Speed Plant Construction,” p. 74.)
|1. Tapping into Lake Michigan. This photo shows the water intake tunnel, located below the lake bed. The tunnel directs cooling water drawn from Lake Michigan to the four existing Oak Creek units and the new Elm Road Units 1 and 2 at the Oak Creek Power Plant. The once-through cooling system is used to cool and condense steam from the steam turbines. Courtesy: We Energies|
The Elm Road expansion project includes a redesigned coal-handling facility. Approximately 17 miles of new rail line and 2.5 miles of conveyors were installed. The old system required the locomotives to be decoupled from the rail cars and for the rail cars to be broken into three separate strings to enable unloading through a rotating car dumper. In addition, the old system required each car to be manually positioned through painstaking, highly skilled operations.
In contrast, the new system allows the locomotive to pull the entire string of up to 130 rail cars through a new rotating car dumper. Once the first car is in position, an “indexer” automatically positions each subsequent car by pulling the entire string of cars through the dumper. After the unloading is completed, a new rail loop allows the locomotive to proceed directly off the site with the empty cars, without having to reverse its direction. The coal-handling system includes an indoor storage facility that has the capacity to store three days’ worth of coal for the older and newer units at the site when running at full load. This storage facility is fully automated, allowing coal to be remotely unloaded and recovered from a central control room.
“As we finish construction of the two new units at Oak Creek, we are increasingly focused on completing a more than $800 million air quality control system upgrade of the existing, older OCPP units. We are also developing renewable energy projects to balance our portfolio and meet the renewable portfolio standards for the state of Wisconsin,” Patulski said.
— Angela Neville, JD, is POWER’s senior editor.